For the most part, flying a drone is legal for recreational purposes, as long as operators follow a few guidelines, like staying below 400 feet. Declining prices — a four-rotor model with a mounted camera can cost as little as $500 — have attracted more buyers. Teal Group, an aerospace research firm, estimates the global civilian drone market to be worth $450 million this year, up 45% from last year.

As the price of drones has fallen and sales have risen, the machines have emerged as central characters in stunts from the puckish to the criminal. In recent months, drone pilots have tried to smuggle contraband into prisons and disrupt sporting events at stadiums. Animal rights groups have turned to drones to stalk hunters as the hunters stalk wildlife. And in France, more than a dozen illegal flights over nuclear power plants have unnerved the authorities.